1. Field of the Invention
The present invention relates to an image forming apparatus such as an MFP (Multi-Function Peripherals) which is a digital compound machine, a copier or a printer, and particularly to an image forming apparatus having a normal mode and a power saving mode, and a control method thereof.
2. Description of the Related Art
In general, in an image forming apparatus such as an MFP, a copier or a printer, reduction in power consumption is attempted from the viewpoint of environmental protection. For example, in an image forming apparatus including a fixing unit, a heat roller and a pressure roller are provided in the fixing unit, and a sheet is passed through between the heat roller and the pressure roller so that an image is fixed on the sheet.
In the image forming apparatus as stated above, in a normal mode, the rated power is supplied to the heat roller to heat the heat roller up to the fixing temperature and the image forming process is performed. Besides, in a standby mode in which the image forming process is not performed for a specified time, power lower than the rated power is supplied to the heat roller, and the heat roller is kept at a temperature lower than that in the normal mode and is placed in a preheat state. Alternatively, there is a case where heating of the heat roller is stopped and a sleep state is generated.
When the standby mode is switched to the normal mode, the heat roller is returned from the preheat state or the sleep state to the fixing temperature, and performs the image forming process. Accordingly, in a period in which the image process is not performed for a specified time, the power consumption can be reduced.
JP-A-2003-233276 discloses an image forming apparatus which can switch between a normal mode and a power saving mode. In this example, there are provided sheet detection means for detecting the presence and absence of a sheet in a paper feed unit, and periphery detection means for detecting a peripheral state of the image forming apparatus, and in a case where the sheet can not be detected, or there is no operator around the image forming apparatus, switching is made to the power saving mode.
However, in the image forming apparatus of the related art, although the shift is made to the power saving mode in the case where the image formation is not performed for the specified time, with respect to the time of occurrence of various errors, a countermeasure for power saving is not taken at all. Besides, also in the example of the above publication, there is no disclosure on a countermeasure for power saving at the time of occurrence of various errors.
That is, in the case where running out of toner or sheet jam occurs, or a serviceman call etc. occurs, in spite of the state where the image forming process can not be performed, the rated power is supplied to the heat roller of the image forming apparatus and the display unit of the operation panel, and wasteful power is consumed.
The invention provides an image forming apparatus which can effectively reduce power consumption even in the case where various errors occur.